1. Field of the Invention
The present invention relates generally to antenna loops of the electromagnetic-induction system, and more particularly to a layout for multi-antenna loops of the electromagnetic-induction system.
2. Description of the Prior Art
Because a handwriting recognition system could replace the mouse, and is more suitable than the mouse to let the user input words and patterns by user""s hands, improvement of the handwriting recognition system is a hot and important field of current computer technology. The original intention of the handwriting recognition system is to replace the mouse. As usual, to enhance the user""s convenience, a handwriting recognition system would usually replace the mouse by both wireless pen and tablet. Herein, the pen nib of the wireless pen usually corresponds to the left button of the mouse. Conventional handwriting recognition systems have been developed for many years, but these products are applied to perform only one function, such as drawing or inputting a word.
In the conventional system with electromagnetic-induction, there are usually a digitizer tablet and a transducer/cursor in the form of a pen or a puck. As is well known, there are two operation modes for determining the position of a pointing device on the surface of a digitizer tablet, wherein one is a relative mode, and the other is an absolute mode. A mouse device operates in a relative mode. The computer sensing the inputs from a mouse recognizes only relative movements of the mouse in X and Y directions as it is slid over the surface on which it is resting. If the mouse is lifted and repositioned on the surface, no change in the signal to the computer will be detected. A common approach uses a sensing apparatus inside the mouse to develop a pair of changing signals corresponding to the longitudinal and transversal movements of the mouse. On the contrary, a cursor device in a digitizer tablet system, such as wireless pen, operates in an absolute mode. If a cursor device is lifted and moved to a new position on its supporting surface, its signal to a computer will change to reflect the new absolute position of the cursor device. Nowadays, various methods have been used to determine the position of a cursor device on the surface of its supporting tablet, wherein one common skill which is applied for the absolute mode is electromagnetic field sensing. Early transducer/cursors were connected to the tablet by means of a multi-conductor cable through which the position and button/pressure information are transferred virtually without any problem. The cordless transducer/cursors in some of the prior arts have attempted to use frequency and/or phase changes to transmit the non-positional status of the transducer/cursor functions such as buttons pushed, pen pressure, or the like. However, if there is no sophisticated processing, frequency and phase changes are very prone to false reading resulting from several outside factors such as metal objects, noise, electromagnetic wave and so on. These problems become more apparent, especially in a larger digitizer tablet. Improvements have also been made in the prior arts to allow a user to use pointing devices on a digitizer tablet system in dual modes of operation that can provide information of either a relative movement or an absolute position under the control of the user.
Usually, a handwriting recognition system is a device with electromagnetic-induction. Conventional electromagnetic-induction device comprises: an electromagnetic pen and a tablet. There is an oscillating circuit that consists of LC in the electromagnetic pen. If the pen point is touched, the amount of inductance will be changed that results in the variation of oscillating frequency. The amount of inductance is increased when touching the pen point and increasing pressure so the variation of oscillating frequency is also increased. Therefore, the variation of the pressure on the pen point can be detected by way of the variation of oscillating frequency. There are two switches on the sidewall of the electromagnetic pen, the emitted frequency of the electromagnetic pen can be changed with the capacitance variation of the LC device that is produced by pushing down or setting free the switches. Furthermore, the tablet comprises a detector, an amplifier and an analog-digital converter. In the conventional tablet, there is a detected loop in the center region of the tablet, with antenna loops located on the double faces of the detecting loop, wherein the antenna loops are equidistantly arranged in order by way of using array. The main purpose of the detecting loop is only applied to receive the electromagnetic wave that is emitted by the electromagnetic pen. When the electromagnetic pen emits the electromagnetic wave, the antenna loops receive the electromagnetic wave, and then the tablet can obtain correlative information by the electromagnetic induction.
In general, antenna loops and layout thereof in the conventional electromagnetic-induction device arranges antennas as check network that are distributed with equidistance in the X-direction and Y-direction of two-dimensional Cartesian coordinates to induce the electromagnetic pen and calculate the absolute position thereof. Refer to FIG. 1A, it shows a layout for antenna loops distributed in the X-direction of two-dimensional Cartesian coordinates, wherein one terminal of each of the antenna loops 110A is connected to each switch (X1 to X25) and the other terminal is electrically coupled with a ground wire 105A, whereby the reduced signal of each of the antenna loops 110A can be detected by controlling the switches (X1 to X25). Because of the inverse proportion of the magnetic field intensity to the square of distance the electromagnetic pen that can emit electromagnetic wave is away from the tablet to result in more and more weak induced signal that is received by antenna loops; on the contrary, the induced signal that is received by antenna loops is an increasing number of intensity when the electromagnetic pen approaches the tablet. Therefore, CPU of the tablet scans one by one and in turn each of the antenna loops to analyze intensity of induced signals that are received by each antenna loops, so as to detect the position where the cordless pen is located and calculate the coordinates thereof.
However, there is an increasing number of antenna loops in the tablet having much larger area so a great amount of antenna switches is necessary. Nowadays, a method that can decrease amount of antenna switches by forming n-shaped sections 120 in the same antenna loop is provided. Refer to FIG. 1B, each of antenna loops (X1 to X9 and XA to XC) distributed along the X-direction of two-dimensional Cartesian coordinates (X, Y), and each of antenna loops (X1 to X9 and XA to XC) comprises a plurality of logical sections 120. Regarding to each of the antenna loops (X1 to X9 and XA to XC) distributed in the same direction, the adjacent logical sections of each logical section 120 therein belongs to different antenna loops (X1 to X9 and XA to XC), whereby the position of electromagnetic pen can be located on the n-shaped section of which the antenna loop is. For example, for the n-shaped section denoted by numbers 120A of the antenna loop X5, its adjacent n-shaped sections 130 and 140 belong to the antenna loops X4 and X6 respectively. However, for the next logical section denoted by number 120B of the antenna loop X5, its adjacent n-shaped logical sections 150 and 160 belong to the antenna loops XC and X2 respectively. Thus, the position of the pen can be decided by the induction voltage produced by physical antenna loops X5, X4, X6, XC and X2 whether the electromagnetic pen (not shown) moves above the n-shaped section denoted by number 120A of the antenna loop X5, or above the n-shaped logical section denoted by number 120B of the antenna loop X5. As foregoing description, amount of the switches in FIG. 1B, such as twenty-five switches, is less than that in FIG. 1A, such as twelve.
In conventional method, it is necessary to be noticed that the distance between two adjacent logical sections in the same physical antenna loop (e.g. the distance L between the adjacent logical sections of the physical antenna loop X5 noted by number 120A and 120B) must be adequate. If the distance is too small, it is possible to make a mis-judgment in deciding the position of the electromagnetic pen. On the other hand, nowadays, digital products are developed toward the aspect of high speed for processing information, which is resulted in electromagnetic interference as high as speed. Generally, there are various digital products around the specific place for using the digital tablet. In terms of the digital tablets with bigger areas that are commercially required, the amount of switches and antenna loops in the digitizer tablets prior art is increased accordingly; therefore, the method that increases amount of n-shaped sections in the same antenna loop is provided to decreased a great amount of antenna switches. Here the method increases length of the antenna loop so as to generate electromagnetic noise, that is, it is easy to be interfered with the electromagnetic noise, and that affects the calculation of the position of the pen that is located on the digital tablet. Furthermore, FIG. 1C shows conventional layout for antenna loops in that the layout of antenna loops distributed along the X-direction and Y-direction of two-dimensional Cartesian coordinates connected a ground wire 105A and 105B respectively and that both arrangement for layout of the antenna loops 110A and 110B overstep the ground wires 105A and 105B, and thus, a predetermined space 170 requires being provided for placing the antenna loops 110A and 110B distributed over the ground wires 105A and 105B, which is located on the boundary region within conventional tablet. Therefore, it is resulted in the limitation for scaling down area, and further, that is difficult to make the panel with small boundary region. In accordance with the above description, a new layout for multi-antenna loops in the electromagnetic-induction system is therefore necessary, so as to solve the problems mentioned from foregoing description.
In accordance with the present invention, a new layout for multi-antenna loops in electromagnetic-induction system is provided that substantially overcomes the drawbacks of above problems mentioned from the conventional system.
Accordingly, it is an object of the present invention to provide a layout for multi-antenna loops of electromagnetic-induction system. The present invention can form antenna loop with sawtooth-shaped section and dummy closed section by n-shaped section with in-phase state to perform the layout of multi-antenna loops, so as to reduce amount of antenna switches and to distribute entire antenna loops along X-axis and Y-axis within the same ground wire. Accordingly, this invention can so reduce the space requirement and the panel area thereof that it scales product""s size down and makes productive cost down. Therefore, this invention corresponds to economic effect and utilization in industry.
Another object of the present invention is to provide a layout for multi-antenna loops of electromagnetic-induction system. The present invention can form an antenna loop with sawtooth-shaped sections and dummy closed sections by n-shaped sections with oppositephase state to perform a layout of multi-antenna loops so as to reduce amount of antenna switches, and in order that the entire antenna loops along X-axis and Y-axis can be distributed within the same ground wire. Accordingly, this invention can avoid jamming antenna loops with electromagnetic noise around the tablet, so that the efficiency of electromagnetic-induction system can be strengthened.
In accordance with the present invention, a new layout for multi-antenna loops of the electromagnetic-induction system is provided in order to achieve the above-mentioned and other objects. The layout of multi-antenna loops in this invention comprises: a plurality of antenna loops distributed along the X-direction and Y-direction of two-dimensional Cartesian coordinates, wherein one terminal of each antenna loop is electrically coupled with an antenna switch and the other terminal is electrically connected to a ground wire; especially, all plurality of antenna loops distributed along the X-direction and Y-direction are electrically connected with the same ground wire. In light of all antenna loops, those are symmetrical antenna loops each of which contains a plurality of substantially identical n-shaped sections, wherein every one of the n-shaped sections is connected with another one of those in the same antenna loop to form a plurality of sawtooth-shaped regions; and further, every two of the plurality of sawtooth-shaped regions are in opposition to each other, and the n-shaped sections of those are face to face from each other so as to form a plurality of dummy closed regions. If the symmetrical antenna loops are in-phase state, that is, the n-shaped sections of the same antenna loops that are adjacent from each other are in-phase state, the plurality of sawtooth-shaped regions are formed by using the plurality of n-shaped sections with the non-interlacing method; if the symmetrical antenna loops are oppositephase state, that is, the n-shaped sections of the same antenna loops that are adjacent from each other are oppositephase state, the plurality of sawtooth-shaped regions are formed by crossing the n-shaped sections from each other with the interlacing method.